Journal ArticleDOI
Energy deposition and microstructural modification in dynamically consolidated metal powders
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In this paper, a model for the deposition of energy at powder particle surfaces during dynamic consolidation is presented, where the average energy flux incident on the surface of a powder particle is estimated to be E/τA where E is the specific energy deposited by the shock, τ is the shock rise time, and A the measured powder specific surface area.Abstract:
A model is presented for the deposition of energy at powder particle surfaces during dynamic consolidation. The average energy flux incident on the surface of a powder particle is estimated to be E/τA where E is the specific energy deposited by the shock, τ is the shock rise time, and A the measured powder specific surface area. This flux is assumed to be constant over the rise time of the shock, falling abruptly to zero for times longer than τ. Solution of the thermal transport equation subject to this boundary condition yields the thermal history within a powder particle having the area‐equivalent diameter D=6/ρ0A, where ρ0 is the solid density. The magnitude of the temperatures and the heating and cooling rates indicate likely material transformations. The penetration of a given isotherm provides an estimate of the volume fraction of material transformed. Good agreement is found between model calculations and measurements of the extent of local martensite formation in consolidated 4330V steel powder an...read more
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Nanocrystalline materials and coatings
Sie Chin Tjong,Haydn Chen +1 more
TL;DR: In this paper, a review of the current developments in fabrication, microstructure, physical and mechanical properties of nanocrystalline materials and coatings is addressed. And the properties of transition metal nitride nanocrystine films formed by ion beam assisted deposition process.
Journal ArticleDOI
Challenges and advances in nanocomposite processing techniques
TL;DR: In this article, the results from numerous studies on various methods for manufacturing nanocomposites with improved properties and retained nanostructures are discussed in detail in detail and recent advances are discussed.
Book
Solid propellant chemistry, combustion, and motor interior ballistics
TL;DR: In this article, the authors present in-depth coverage on a wide range of topics including advanced materials and non-traditional formulations; the chemical aspects of organic and inorganic components in relation to decomposition mechanisms, kinetics, combustion and modelling; safety issues, hazards and explosive characteristics; and experimental and computational interior ballistics research, including chemical information and the physics of the complex flow field.
Journal ArticleDOI
Dynamic compression of materials: metallization of fluid hydrogen at high pressures
Abstract: Dynamic high pressure is 1 GPa (10 kbar) or greater with a rise time and a duration ranging from 1 ps (10−12 s) to 1 µs (10−6 s). Today it is possible in a laboratory to achieve pressures dynamically up to ~500 GPa (5 Mbar) and greater, compressions as much as ~15-fold greater than initial density in the case of hydrogen and temperatures from ~0.1 up to several electronvolts (11 600 K). At these conditions materials are extremely condensed semiconductors or degenerate metals. Temperature can be tuned independently of pressure by a combination of shock and isentropic compression. As a result, new opportunities are now available in condensed matter physics at extreme conditions. The basic physics of the dynamic process, experimental methods of generating and diagnosing matter at these extreme conditions and a technique to recover metastable materials intact from ~100 GPa shock pressures are discussed.Results include (i) generation of pressure standards at static pressures up to ~200 GPa (2 Mbar) at 300 K, (ii) single-shock compression of small-molecular fluids, including resolution of the recent controversy over the correct shock-compression curve of liquid D2 at 100 GPa pressures, (iii) the first observations of metallization of fluid hydrogen, nitrogen and oxygen compressed quasi-isentropically at 100 GPa pressures, (iv) implications for the interiors of giant planets within our solar system, extrasolar giant planets and brown dwarfs discovered recently and the equation of state of deuterium–tritium in inertial confinement fusion (ICF) and (v) prospects of recovering novel materials from extreme conditions, such as metastable solid metallic hydrogen. Future research is suggested.
Journal ArticleDOI
Dynamic Consolidation of Metal Powders.
TL;DR: In this article, a brief review and assessment of the dynamic consolidation of metal powders is presented, focusing on the relationship between the shock-wave physics during consolidation and the initial and final metallurgical states of the compact.
References
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Book
Conduction of Heat in Solids
H. S. Carslaw,John Conrad Jaeger +1 more
TL;DR: In this paper, a classic account describes the known exact solutions of problems of heat flow, with detailed discussion of all the most important boundary value problems, including boundary value maximization.
Journal ArticleDOI
Shock Waves and High-Strain-Rate Phenomena in Metals
TL;DR: The proceedings of EXPLOMET 90, the International Conference on the Materials Effects of Shock-Wave and High-Strain-Rate Phenomena, held August 1990, in La Jolla, California, represent a global and up-to-date appraisal of this field as discussed by the authors.
Journal ArticleDOI
Shock wave study of the α ⇄ ε phase transition in iron
L. M. Barker,R. E. Hollenbach +1 more
TL;DR: In this article, the free surface velocities of Armco iron specimens and impactors were obtained with the VISAR laser interferometer instrumentation system, which provided new information concerning the rate effects associated with the α → e polymorphic phase transition at 13 GPa, material strength and release wave speeds at 10 and 40 GPa.
Journal ArticleDOI
The properties of stainless steel compacted dynamically to produce cold interparticle welding
TL;DR: In this article, the impact of a high-speed punch on metal powder has been shown to result, under optimized conditions, in interparticle melting and welding, and a strong compact is thus obtained which requires no subsequent thermal treatment.